Photoinduced multistep energy and electron transfer in an oligoaniline-oligo(p-phenylene vinylene)-fullerene triad

A donor-donor-acceptor triad, OAn-OPV-C-60, With a redox gradient has been synthesized by covalently linking an oligoaniline (OAn), an oligo(p-phenylene vinylene) (OPV), and a fullerene (C-60) in a nonconjugated linear array. Photoluminescence and femtosecond pump-probe spectroscopy studies reveal that photoexcitation of any of the three chromophores of this triad in a polar solvent results in formation of the OAn(-)OPV(+)-C-60(-) charge-separated state, after an efficient ultrafast ( 1 ns) due to weak electronic coupling between the distant redox sites in the excited state. The stabilization gained is more than I order of magnitude in time. The experimental results are found to be in qualitative agreement with Marcus theory. In thin films, the OAn(+)-OPV-C-60(-) state is formed at a higher rate and in higher quantum yield than in solution.